Gaseous developing tank construction for diazotype materials



Oct. 28, 1958 F. H. FRANTZ 2,857,831

GASEOUS DEVELOPING TANK CONSTRUCTION FOR D IAZOTYPE MATERIALS Filed July 18,1955

INVENTOR FREDERICK H. FR NTZ YG-QMZALB ATTORNEYS United States Patent GASEOUS DEVELOPING TANK CONSTRUCTION FOR DlIAZUIYlE MATERIALS Frederick H. Frantz, Binghamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corperation of Delaware Application July 18, 1955, Serial No. 522,771

2 Claims. (Cl. 95-94) This invention relates to developing apparatus for sensitized materials and more particularly to a gaseous developing chamber used in connection with diazotype copying material.

In the art of reproduction utilizing diazotype sensitized materials, alkali vapor is commonly used for development of the latent image after the material has been exposed under proper lighting conditions. The developing gas, which, in most cases, is vaporized aqueous ammonia, may be applied to the material in various Ways but generally the sheet material is passed tightly against a perforated wall of the developing chamber so that the gases exuding through the perforations of the Wall reach the material.

When a gaseous developer contacts the metal portions of the developing chamber, particularly the perforated wall, it will often condense on the inner surface and will adhere to it for some time. This is detrimental because the developer condensate in the form of a droplet may contact the material as it passes over the perforated wall causing blotches in the finished print. In addition, the coefficient of friction on the stainless steel is such that the material will often stick to the metal or may be scratched thereby.

It is a primary object of this invention to eliminate the above disadvantages by providing a surface which has a low coefiicient of friction over which the material is passed.

Another object of the invention is to provide a material treating surface for the developing chamber on which the gaseous developer will not condense.

A particular feature of the invention is that the treating surface provided for the material is a component part of the developing tank and may be easily removed for the purpose of cleaning.

Other objects and features will be apparent from the following description of the invention, pointed out in particularity in the appended claims and taken in connection with the accompanying drawing in which:

Fig. l is a perspective view of a developing chamber, in accordance with the invention, with the perforated wall in place;

Fig. 2 is a front elevational view of the perforated wall in the form of a panel which fits over the developing chamber;

Fig. 3 is a perspective view similar to Fig. 1 with the perforated panel removed; and

Fig. 4 is an enlarged cross sectional view of the perforated panel showing that it is made of plastic material.

Referring to the drawing, the developing chamber comprises an enclosure having a top wall 5, bottom wall 6, side walls 7 and 8 and back wall 9. These walls are generally made of metal, such as stainless steel, inasmuch as, within the chamber, the developing gas is formed by evaporation requiring considerable heat. The evaporator mechanism is not shown here since it has no particular reference to the invention.

The front Wall 11 of the developing chamber consists of a perforated panel, as seen in Fig. 2, which is made of a high temperature plastic material as illustrated in the cross section in Fig. 4.

While a metal surface may be employed for the perforated wall of the developing tank, as has been the practice in the past, there are certain inherent disadvantages. As mentioned before, condensation is apt to form on the rapidly cooling metal surface which is in contact with a sleeve 12 which is generally made of rubberized canvas and which moves over the rollers 13 and 14. The sleeve 12 is used to move the copy material past the perforated wall and in contact therewith so that the gases may reach the sensitized surface of the material. The resulting condensation of the vapors thus forms droplets which may, at times, exude through the perforations and mar the material. Moreover, the friction between the material (generally paper) and the hard surface of the metal may damage the sensitized surface of the paper.

In accordance with the invention, the perforated Wall is made as a separate removable panel of high temperature plastic material such as poly (tetrafluoro ethylene). The latter is also known by the trade name Teflon. Various means may be provided for supporting the perforated plastic panel 11 to form the front wall of the developing chamber.

A simple but eflicient way is shown in the figures, particularly Fig. 3, where the side walls 7 and 8 extend toward the front of the developing chamber and support guide plates 16. The channel 17 formed between the guide plates 16 and the frame 18 permits the slidable support for the panel 11 which, in this manner, may be quickly inserted and also removed for the purpose of cleaning without disturbing the rollers 13 and 14.

The plastic material of the panel provides a smooth gliding surface for the sensitized material, whether paper or foil, so that it will not be marred by the friction produced as it passes over the perforated panel.

I claim:

1. A stationary developing chamber for diazotype material wherein an alkaline developing liquid is vaporized, comprising an enclosure having metallic top, bottom, back and side walls, said side walls extending toward the front of the chamber beyond the top and bottom walls, guide plates attached to the inner surfaces of the extended portions of the side walls forming vertical channels one on each side of the side walls, a perforated panel slidably positioned in said channels and forming the front wall of said enclosure, whereby said perforated panel may be removed and replaced in position by a sliding movement in a vertical direction, said perforated panel formed of high temperature resisting plastic material whereby to minimize condensation of the vapors issuing through the perforations and to prevent scratching of the front or sensitized face of the material to be developed when said face is moved in contact with said panel and a movable sleeve supported adjacent the perforated panel and positioned to contact the back of the material to be developed and move said material across the outer face of the perforated panel in frictional contact therewith.

2. A stationary developing chamber as recited in claim 1 wherein said perforated panel is formed of polytetra fluoro ethylene.

References Cited in the file of this patent UNITED STATES PATENTS 2,350,257 Steglieh May 30, 1944 2,384,155 Brunk Sept. 4, 1945 2,515,144 Trump et a1. July 11, 1950 FOREIGN PATENTS 598,921 Great Britain Mar. 1, 1948 

